Electronic control circuits



Aug. 8, 1950 M. E. BNI-:Ns

ELECTRONIC CONTROL CIRCUITS Filed Sept. l2, 1944 TIPI I I wh HT. n HAN a..

00000.00 ...0H l. ...GUCCI S, V., I@ C ww-r CB2@ nct S60/AM Y@ ..6 SMH ,a M y b Patented Aug. 8, 195'() ELECTRONIC CONTRGL CIRCUITS Maurice E. Eivens, Schenectady, N. Y., assigner to General Electric Company, a corporation of New York Application September 12, 1944, Serial No. 553,723

(Cl. Z50-27) 24 Claims.

My invention relates to electric control circuits and more particularly to improved timing or cycle counting circuits. While not limited thereto, my invention is particularly well adapted for use in connection with the control of intermittently energized load circuits, such as the welding transformer of resistance, spot or seam welding systems.

As the commercial application of resistance welding has increased, there has been an increased need for improved timing circuits which are unaffected by voltage fluctuations, and preferably for circuits operating on a cycle counting principle rather than merely timing intervals by capacitor charging or discharging. Many electrical and mechanical timing systems have been emp-loyed but most of these have lacked flexibility It is another object of my invention to provide I a new and improved electronic timing circuit.

it is still another object of my invention to provide a new and improved electronic cycle counting system.

lt is a still further object of my invention to provide a new and improved timing circuit which oiiers flexibility of adjustment and consistent timing despite supply line voltage fluctuations.

In accordance with the illustrated embodiment of my invention, the energization of a load circuit of an alternating current supply is controlled by a pair of reversely connected electric valve means. The cycles of the supply line voltage during which the electric valve means are conductive correspond to the cycles during which an alternating 1 current turn-on voltage is supplied to the control members of the electric valve means by an improved timing or cycle counting circuit including a plurality of pairs of reversely connected electric valves which are arranged to conduct in leading and trailing relationship. The alternating current turn-on voltage is supplied by the conduction of one of these pairs of reversely connected electric valves. When operating to time a spot Weld, the number of cycles during which current is supplied for one energization of the load circuit is determined by the number of successive cycles during which this pair of reversely connected electric valves is conducting. When operating to time a seam weld, the number of pairs of electric valves in the timing circuit is equal to the maximum number of cycles of conduction and nonconduction of the repetitive pattern to be supplied to the load circuit. The number of cycles of conduction for the pattern is determined by the number of the valves initially rendered conductive. After conduction is initiated, it progresses from valve to valve in sequence at the rate of one valve per half cycle of supply circuit voltage. The timing is effected, therefore, entirely by the cycle counting operation of the leading and trailing electric valves and is independent of variations in the supply line voltage.

For a better understanding of my invention, reference may be had to the following description taken in connection with the accompanying drawing, in which the single gure is a schematic repre-sentation of one embodiment of my invention, and its scope will be pointed out in the ap'- pended claims.

Referring now to the drawing, I have shown my invention embodied in a system for controlling the energization of a load circuit, such as a resistance welding transformer l having the primary winding 2 thereof energized from an alternating current supply line 3 through a pair of electric valves 4 and 5 which are reversely connected in parallel between the supply circuit and the primary winding of the welding transformer. The electric valves Il and E may be any of the types well known in the art such as those employing a mercury pool type cathode cr mercury vapor, and, as illustrated, each comprises an anode E, a cathode l, a control member or grid 8 and a screen grid 8 which is preferably connected directlyi to the cathode. The control member of each of the electric valves 4 and 5 is energized with the resultant of four components of voltage to determine the cycles and the instants in the cycles of the supply line voltage that conduction is initiated. These components include an alternating current hold-off voltage, a self-biasing hold-ofi` voltage, a periodic or alternating turn-on voltage supplied by the timer control to determine the cycles during which the load circuit is energized and a peak voltage of adjustable phase which determines the instant in the cycle at which conduction is initiated.

Referring now to the circuit of the control 3 member of the electric valve 4', it may be traced from the cathode through the secondary Winding 9 of a transformer I0, the secondary `.Winding II of a transformer I2, a secondary Winding I3 of a peaking transformer I4, a self-biasing circuit including :parallel connected resistor I and capacitor IS, and a current limiting resistor Ii. The transformer I0 has the primary winding Iii thereof energized 'from the alternating' current supply 3 and provides by winding 5 a voltage 186 out of phase with respect to the anode voltage of electric valve 4. The Winding III of transformer I2 provides the periodic or alternating current turn-on voltage during periods that the primary winding I3 thereof is energized. by the timing circuit designated generally by the nu-1 meral I9. The primary winding 2B of the peaking transformer lli is energized by a voltage of adjustable phase withrespect to the voltage of supply circuit 3 by means of a .phase shifting circuit including a secondary winding 2| of transformer I9 having a midtap 2li, resistor 22 and capacitor 23. Resistor 2'2 and capacitor 23 are connected in series and across the end 'ter- .minals of transformer winding '2l to provide a voltage between the midtap 2 of transformer winding 2l and the common terminal '25 of resistor 22 and capacitor 2'3 fwhichis readily adjusted by adjusting the .magnitude of resistor 22. rIhe Vprinfiary winding of the 'tnansformer I4 is energized from the terminals '24 and 25 through a series circuit including a resistor '25 and a filter including -inductance 21 and a capacitor '28. This circuit for producing peaked. voltages of adjustable rphase is fully described and claimed in Levoy Patent 2,246,177, dated June 1'7, 194'1, and .assigned to the assignee of the present invention. The resistors 29 and 3D are connected, respectively, across the secondary windings I'I and I3 to maintain a reasonablylovw impedance in the circuit of control member during periods that the transformer I-2 is'deenergized and during periods that transformer I4 is unsaturated. In order to insure consistent operation of electric valves 4 and 5 in accordance with the control voltages impressed on the control members thereof, suitable lter capacitors 3.1, 32 and 33 are provided. Capacitor 3l is connected directly between the control member B and vcathode I; capacitor 32 is connected across the terminals of the winding 9 which impresses the hold-off voltage on control member 8, and capacitor 33 is connected to the cathode of electric valve 2i' and alternating current supply circuit 3 'is provided with a secondary .Winding 39 having end terminais l0 and -tiI and intermediate terminals I2 and i3 connected with conductors bearing the same reference numerals to provide four diiferent levels of alternating voltage. These voltages are employed for energizing electric valves EL? to 5I, inclusive, `whichare arranged in .pairs in each of which the electric valves are connected in inverse relation. The valves lili to 5l are preferably of the type employing an ionizable medium such as a `gas or `a vapor. Electric valves 44, 46, I8 and 50 have the cathodes thereof connected with the alternating current supply conductor 43 and the anodes connected with the alternating current supply conductor 45. Each of the anode leads is connected to the conductor 4B through an inductance which, in the case of valves lili, :26 and 5B, is designated by the numeral 52, and in the case of electric valve K8 is provided by the prito a point in the -control circuit between the v self-'biasing circuit including resistor l5 and oapacitor I6 and the secondary winding I3 of the peaking transformer. In the Yabove description only the lcircuit of the control member of electric valve 'i is described. The control circuit for the control member of electric valve 5 is in gen- 1;.

eral the same and corresponding parts have been given the same reference numerals. Instead of the transformer I2, the control memberof electric valve 5 is energized by the secondary windhaving a primary winding 38 energized from the .mary )Winding IB of the transformer I2. The -cathodes of electric Valves d5, El, '39 and 5I are connected with `the alternating current supply conductor @2, andthe anodes of these'valves aire connected for energization from the supply conductor i. The anode circuits 'of valvesli5, '41 and El each include ,a reactor 53 while theinductive reactan'ce in .the anode circuit `of valve "11:9 is provided by the .primary winding of transformer 35. The inductive reactance in the 'anode-cathode circuits of lvalves lili to 5I, inclusive, extends the 'period of conduction with respect to the applied voltage 'to improve 'the leading'aand trailing operation or" the valves which Will be described at .a later .point inthe specification.

In order to facilitate setting the system for different spot' lengths 'anddiierent weld patterns for seam Nvelding, double pole double throw 'switches "Ell, .55 and Y5t and single pole, single throw switches "5I and 58 are provided. These switches determine the number of valves which aire employed, the 'number of Valves in which conduction is initiated originally and whether the valves conduct in sequence only once as `for vspot rwelding or whether-'they trail one another in a closed loop las lfor seam melding. The manner in which the different circuit relations are established by operation of 'the switches 5t to 58, inclusive, lwill become more apparent as `the description Vproceeds.

The control members of valves 45, 4l, '4t and 5i are connected directly with the anodes of valves t, 55, 233 and 50, respectively, through current .limiting resistors 59. The control member of valve i8 is .connected with the anode of valve @El While the control member of valve I3 is connected with the anode of valve '455 through a contact 'G of switch 5, or to the anode of valvelg through ra .contact 5I oi switch 54, a conductor 35, contact .i555 of switch'55, contact of switchEB and a con- .dnctor .58 or to the anode of valve '5l through a vcircuit extending -:from conductor '65 through con- .connected with the .anode of valve t9 throughconductor 5S and contact 5l of switch 53. Current .limiting resistors .59 are also provided in circuit with the control members rof Valves 1115, 5.1, 49

vand 5|..

From 'the preceding description of the energizing circuits for the electric valves iJi, in-

5. elusive, it will be apparent that the control members of electric valves 44, 45, 48 and 59 are energized through circuits each of which includes the voltage of winding 39 appearing between conductors 4| and 43. This voltage is 180 degrees out of phase with the voltage impressed on the anodes of the valves and maintains these valves normally nonconductive. In a similar manner, the valves 45, 4l, 49 and 5l are maintained normally nonconductive by the voltage of winding 39 appearing between conductors 49 and 42. From the preceding description, it is also apparent that the connection ci the control members oi the successive valves with the anodes of the preceding valves provides a system in which conduction once initiated will advance from Valve to valve at the rate of one valve per half cycle of the supply circuit voltage. In order to determine the spot length or weld pattern for seam welding, I provide means for initially rendering selected ones of the vvalves conducting. In the illustrated embodiment, this means is provided by a transformer 'il having the primary winding 'l2 thereof energized under the control of an electric valve 13 and the secondary winding 'I4 connected to impress a voltage across a resistor 'l5 which is connected between the conductor 4l and a conductor 'it which may be considered an initiating bus. From an inspection of the drawings, it will be seen that the control members of selected ones of the electric valves 44-59 may be connected with the initiating bus 'it by means of the switches 54, 58, inclusive. For example, with switch l in the lower position, as shown, the control member of electric valve 4t is energized by a voltage across resistor 'I5 in addition to the holdoi component of alternating voltage between conductors 4l and 43. The electric valve 'i3 which controls the energization of the transformer 'H is preferably of the type employing an ionizable medium and is connected for energization from the voltage of transformer winding 39. As indicated on the drawings, the cathode is connected with conductor 43 and the anode is connected to conductor 49 through the primary winding 'l2 of transformer ll, a normally open contact l5 of an initiating relay 'l5' and a capacitor ll'. The capacitor is provided so that a single steep wave front pulse of current is supn plied to the primary winding l2 for each operation of the initiating relay l5. The conduction of valve 13 is initiated at a predetermined point in the alternating voltage wave supplied by transformer winding 39 by a peaking transformer 18 having a primary winding I9 connected in series with a reactor 80 and across the terminals 49 and 4I of winding 39. A secondary winding 8| of the peaking transformer isY connected between the control member of electric valve i3 and the conductor 4l by a circuit including a normally open contact 82 of the initiating relay 'l5'. A resistor 83 is provided across the secondary winding of the peaking transformer and a current limiting resistor S4 is connected in series with the control member of the electric valve 13. Energization of the operating coil 85 of the initiating relay from the alternating voltage supplied by conductors 49 and 4l is controlled by a manual initiating switch SS. A discharge circuit for the capacitor I7 is provided by a shunt circuit including a resistor 81 and a normally closed contact 88 on the initiating relay. With the initiating circuit described, it will be apparent that closure of switch 86 provides a voltage impulse between conductor 4I and initiating bus '16, and that only one voltage impulse is provided for each closure of the initiating switch regardless of the length of time that the switch is maintained closed. The initiating relay 'l5' is also provided with a normally closed Contact 89 in a circuit connecting the control member of electric valve 48 with the conductor 4I to prevent further conduction by valves 43 and 49 after deenergization of the initiating relay. A suitable current limiting resistor 96 is included in this circuit. Since valves 48 and il conduct, respectively, ,for half cycles corresponding to the half cyclesof conduction of the power valves 4 and 5, the Contact 89 provides means for terminating conduction -by valves 4 and 5 upon release of the initiating switch 86.

The system described above including four pairs of reversely connected electric valves may be set to time spot welds of 1 to 3 cycles in length and to establish weld patterns for seam welding in which the sum of the cycles of conduction and nonconduction of the repetitive patterns is 4 cycles or less. The range of operation of the system may be increased by increasing the number of pairs of valves employed. A ,better understanding of the features and advantages of my invention may be had by a consideration of the operation of the illustrated embodiment of the invention for .both spot and seam welding operations. First, the operation of the system for seam welding with a weld pattern of 3 cycles on and 1 cycle off will be considered. For this operation, switches 54 to 58, inclusive, are in the position illustrated on the drawing, that iS, With SWCh 55 in the up position and the remaining Aswitches in the down position as illustrated on the drawing. With the alternating current supply circuit 3 energized and the cathodes of all the electric Valves at operating temperature, all of the valves will remain nonconducting due to the holdoif voltages impressed on the control members thereof. The main power valves and 5 are maintained nonconductive by the holdoff voltage supplied by transformer ill. Valves Lilil, inclusive, are maintained nonconductive by the alternating holdoif voltages provided by the portions of the transformer winding 39 appearing between conductors 40 and 42 and 4l and 42, and valve 13 is also maintained nonconductive by the voltage between conductors 4l and 43, The instant in the half cycles of voltage of the supply circuit that electric valves 4 and 5 are to be rendered conducting is predetermined by the phase relation of the peaked Voltage produced by transformer I4 which is controlled by adjustment of the resistor 22 of the static phase shifting circuit. To initiate operation of the welder, initiating switch 86 is closed to energize the operating coil 85 of the initiating relay 15. Operation of relay 15' closes contact 16 to complete the anode-cathode circuit of electric valve 73 and il; opens contact 89 to release the control member of valve 48. Operation of relay 'l5' also closes contact 82 to connect to secondary winding 8| of peaking transformer across the resistor 83 in the control member circuit of valve 13. This irnpresses a peaked Voltage on the control member at an instant determined by the reactor 80 and 7 the lowerA section of .transformer winding. Seto. conductor 4 I., through resistorY l5, the riglfithand` contact of switch 54, reactor: 53, the left-hand" contact of switch 54 andther current limiting resistor- 59. When valves-461y48iand lltconduct, 5: the control members otvalves. 41,1 49 and. ETlare. broughtsubstantially tothe voltage of theconAV ductor 43v since these control'members are connected respectively with theranod'es :off valves 451, 43- and 5U. This places valves 4H', 49 and` 5l4 in condition toconduct as. soon asY the anode-A cathode voltage' impressed on thesevr valves: re verses. In this manner, valves V417, `49 andi 5l trail valves 46, 48 and 50-anditheconduction initiated in the..three-valves spaced alternately in-` the 15 sequence continues to'. advance aroundthe loop. including valves -44l to-51l at` the rate of l valve per half cycle oi? voltageot the suppl-yfcircuit.y During the thi-rd'halt cycle atterinli-tiation,Y electric valve 43A Will again befvrenderedconductive and during the iourth hair' cycle electric valve- 491 will be rendered conductive. The firstperiod` of energzation of the seam weldf will be onlyl twoA cycles in duration but from then onlvalvesnl-l and 49 each conduct-.for three successive half cycles by the trailing actionlof `the electric valvesv i4- 5.5. Since conduction by electric valve 48' energizes transformeri2r to producea-turn-on voltage acrossv resistor- 29m control member circuit of electric valve.l 4V andi conduction by valve 49' energizesntransformer. 35 to produceva turn-on voltage acrossresis'tor '29. in Pthecon-trol member circuit of electricvalve 5`, it isapparen-t that the halt cycles of. conductionby valves and 5 correspond exactly tothe halflcyclesof conduction by electric valves 48 and 49. Thepattern of conduction` of valves 48=Y and 49 is, therefore, thev Weld pattern. It` will be understood that the time in-the cycle` of thefalternating voltage that conductionof valves-4 and 5Lis initiated is adjusted independentlyl of valves 48. and 49 by adjustmentof the phase shifting circuit including resistor 22'. Thus, it i'sseen that the circu-it `Hloperates on acycle counting principle and th-atthe duration `ofthe periods ot i. energization and deenergization off' the welding transformer l are accurately measured in half cyclesl independently of supply line voltage fluctuations. In` theta-blebelow arel shoW-n the positions of switches'lii'to, inclusi-ve, for-different seam welding patterns which maybe preestablished with the'illustrated embodiment of the invention.

ffii

SEAM VV'I-BI'J'DI'NG Table YI age supply of valve 5l.

lv by conduction of valve 4'. During the nextfhali cycle valve 49 conducts and the opposite half cycle is supplied to the Welding transformer. During .the first cycle after initiation While. conduction advances. from valve 46 to valve 48, conduction originally initiated in valve 5U advancesv to valve 44. During the cycle of energization of the load which corresponds to the cycle during which valves 48 and 49 conduct, conduction advances from valve 44 to valve 4t. During the succeeding cycle valves '48- and 49 are nonconducting, establishing a cycle oi deenergization of the load circuit. During this cycle conduction progresses from valve 46, through valve 4l, to valve t3r at the beginning of the next succeeding cycle to initiate another period of energization of the load cir-V cuit. In a similar manner, the other patterns indicated in the table may be established by placing the switches in the positions indicated. The second pattern, namely one cycle on and two cycles oit, is a pattern having a total of three cycles` which is not a factor of the total number of valves shown in the drawing. lt is therefore necessary to effectively remove one pair of the valves from Vthe valves which conduct successively in a loop to establish this pattern. This is accomplished by placing switch. 55 in the down or out position which eiiectively removes valves 53 and 5l by interrupting the anode-cathode volt- For this pattern, electric valve 4S only is initiated. Fora pattern of one cycle on and three cycles ofi, all of the electric valves are employed and' only valve it is initiated. rlhe operation of the systeraior the other patterns is believed to be apparent from a consideration of the information included in the table. From the above descriptionV and a consideration of Table I it is apparent that the total number of pairs of valves connected to conduct in sequence in a closed loop is equal to the length in cycles of the respective patternsv to be established or is an integral multiple thereof. It is also ap-l parent that this is determined by the number or numbers and location in the sequence of the valves initially rendered conductive.

In the above description of the operation of the system for seam Welding, it is pointed out that the electric valves trail each other in a vclosed loop as long as the initiating switch B remains closed. When switch 86 is released, initiating relay 'l5' drops out to close its contact 89, thus connecting the control member of electric valve 48 directly with the alternating current supply Switch Position Weld Pattern l Conduction Valves' Trailing iu a Originally Closed Loopv Initiated in Valves 3 on l oil 46 and 48.

46 and 48.

46, 48 and 50.

For. a patternlotone cycle :on and one cycle oit) switches 54 and 53:!are in the down position, switches. 55 and "in the .upqziosition.,` and switch 5B in the down or seam position. With this ar .t rangement, electric valves 4G1and 7594 arey initially renderedl conductive. After one-- cycle of the supply circuit voltage thecondtiction` initiated in valve 46 has causedeonduction orI valve Ato conductor 4l to prevent further" conduction by this electric Valve and in this way terminate the supply of current toy the load-circuit.

From the foregoing description of the operation o-S the timing circuit i9 for timing a seam Weld', it is apparent that each pair of valves has the same pattern of conduction as the power valves 4and 5 which supply the welding load effect energization o` thewelding transformer le circuit and that the patterns of the different pairs are displaced with respect to one another' by integral cycles of voltage or" the supply circuit. This feature of the timing circuit i9 makes it possible to operate a plurality of seam Welders operating on the same weld pattern in such a manner that the current demand on the supply circuit is evenly distributed. For example, ii one Welder or a group of Welders is controlled from the electric valves 48 and 49, as previously de scribed, and these Welders are, for example, operating on a pattern of two cycles onmtwo cycles ofi, another group of Welders controlled by valves 44 and 45 would operate with a weld pattern of two cycles on-two cycles off but with the pattern displaced two cycles with respect to the Welders controlled by valves 48 and 49. In this manner the maximum demand on `the load cir cuit 3 at any time is the demand of one of the groups of Welders. To accomplish this control it is only necessary to employ initiating transformers similar to transformers 2 and 35 in place of the reactors 52 and 53 in circuit with valves 44 and 45, respectively. The secondary windings of these transformers have been designated by the nu- `merals 9i and 92, respectively. rihese windings also carry a legend designating that they are associated with Welder No. 2. It will be appreciated that these secondary windings are connected in the control circuit of a Welder which is a duplicate or" the one illustrated in full and designated Welder No. l in the same manner as control transformer windings H and 34. Similarly, ii a number oi seam Welders were to be operated with a pattern of one cycle on-two cycles oi, they would be divided into three groups with each group being controlled in accordance with a different pair of electric valves which are arranged to conduct in succession. lIhat is, one group would be controlled by valves 4@ and 45, a second group by valves 4S and lil, and a third group by valves 43 and 49.

When the system is operated to time a spot Weld, switch 55 is placed in the up position and switches 54, 55, l and 58 are placed in the up or down position, in accordance with the following table, to time spot welds of diierent spot time a spot weld there are two notable diiler ences as compared With the operation for seam welding. First, the electric valves trail each other starting with a leading valve only once. That is, the Valves trail one another in a single sequence rather than iny a closed loop. Second, the number of pairs of valves connected in sequence is one greater than the spot length, measured in cycles.

From an inspection of Tables I and II, it will be noted that switch 54 is in the down position in all cases except for spot welding with a one cycle spot length. Since for this operation it is only necessary that electric valve 46 not be initiated, it would be adequate if switch 54 were a single pole, single throw switch the same as switches 51 and 58. However, the switch 54 connectedV as illustrated is necessary if six pairs of valves are employed to make it possible to establish seam weld patterns of six cycles duration. 'I'he extension of the system to time six cycles can be made by simply adding two pairs of electric valves between valve 41 and valve 48 with single pole, single throw switches connected in the same manner switches 5'! and 58.

While I have shown and described a particular embodiment of my invention, it will be obvious to those skilled in the art that changes and modifications may be made without departing from my invention in its broader aspects, and

I, therefore, aim in the appended claims to cover all such changes and modifications as fall Within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. In. combination, an alternating current sup-l ply circuit, a plurality of electric valves each in cluding an anode, a cathode and a control member, means connecting the anode-cathode circuits of said electric valves for energization from said supply circuit so that half of said electric valves are energized with voltage of one polarity and the other half of said electric valves are energized with voltage of the opposite polarity, means energizing the control members of each of said electric valves in response to conduction by a diiierlengths, ent one of said electric valves for rendering said SPOT WELDING Table II t Switch Position Cinductilon spo Tlgln Y Length Valves m Sequence Initiated in 54 57 58 55 56 Valves l Cycle..- Up Down Up Down Spot All but 44, 45, and 5l 48. 2 Cyclc Down do do rlo do All but 50 and 51 46 and 48. 3 Cycle do do do Up do All 44. 46 and 48.

For a spot weld of a single cycle duration, electric valves conducting in sequence by trailing switches 54 and 5B are up and switches 55 and 5l are down. IIhis effectively removes valves 44, L15 and 5t, 5I from the system and provides for the initiation of conduction in electric Valve 48. After one cycle oi the supply circuit voltage conduction in electric valve 4S is complete, energica* tion of the load circuit is interrupted since no further trailing action in the system of electric valves takes place. This results from the position of switch 5t which interrupts connection from the anode oi electric valve 49 which is otherwise completed to the control member of valve 5B, valve 44, or Valve d5, dependent upon the number of pairs of Valves effectively connected one ancther, and means for establishing a repetitive pattern of conduction and nonconduction of of said electric valves by simultaneously applying to the control elements of more than one ci said electric valves a voltage which renders said more than one electric valves initially conM ductive, said repetitive pattern of conduction and nonconduction of said one of said electric valves being measured in half cycles determined by number and location in the sequence of said more than one electric Valves initially rendered conductive.

2. In combination, an alternating current sup ply circuit, a plurality of electric valves each inin the system. In the operation of the system to cluding an anode, a cathode and a control member, means connecting vthe anode-cathode yreircuits of said electric valves for-energization from 'said supply circuit `so that half -of :said electric valves are energized with voltage of one :polarity and :the other half oi said electric valves areV cn- Vergize'd with voltage of the opposite -polarity,

vmeans energizing the control members of each of said electric valves in response to conduction by a diierent one of said electric valves `for ren-- dering said electric valves conducting 'in sequence `by trailing one another in a closedk loop at the rate o'f -one electric valve per halffcycle of the voltage of the supply circuit, and means for establishing a lrepetitive pattern of conduction and nonconduction of one of said electric valves by simultaneously applying to the control elements of more than one of said electric valves a voltage which v.renders-said more 'than one electric valves initially conductive, said -frepetitive pattern of conduction and ncnconduction of saidone of said electric valves being measured in half cycles 'determined by number and location in the sequence ofvsaid more than one electric valves initially rendered conductive.

3. In combination, an alternating Vcurrent supply-circuit, aplurality of electric valves each including an anode, a cathode and a control member, means connecting the anode-cathode circuits iof said yelectric valves for energization from said .supply circuit so that half of vsaid electric valves are energized with voltage of one polarity and "the other half of said electric valves are energized with voltage of the opposite polarity, means for Aenergizing the Vcontrol member of each -of said electric valves in response to'conduction by la different one of said electric valves so that said electric valves conduct lin sequence by trailing one another in a closed loop at the rate of one electric valve per half cycle o'f the voltage of the supply circuit, means for simultaneously applying a voltage to the control elements of a predetermined number of said electric valves for rendering Asaid predetermined number of electric valves conducting and thereby establishing a repetitive pattern of conduction and nonconduction 'by one of saidelectric valves measured in half cycles deiterm-ined by the number and location in the sequence of said electric valves initially rendered conductive, and switching means for connecting in said loop a number of pairs of said electric valves equal to the number of cycles -or lan integral multiple thereof of the pattern to be established.

4. In combination, an alternating current supply circuit, a plurality of electric valves each Yincluding an anode, a cathode and a control member and the number of said electric Valves being equal to the number of half cycles in a repetitive pattern of conduction to be established by said -electric valves, means connecting the anode-cathode circuits of said electric valves for energization from said supply circuit so that half of said electric valves are energized with voltage of one polarity and the other half of said electric valves are energized with voltage of the opposite polarity, means for energizing the control members of eachof said electric yvalves in response to conduction by a different one of said electric valves so that said electric valves conduct inl sequence by trailing one another in a closed loop, means for pre-establishing the number and location in the sequence of selected ones of said electric valves vWhosein'itial Vcenchicticn establishes the pattern of --conduction oi' all of said electric valves, and

'means for simultaneously 'applying to the con- 'trol members of :said selected electric valves .a

- voltage which renders said selected electric valves initially conducting.

5. In combination, circuit controlling means for transmitting alternating current vto a load circuit 'from an alternating current supply circuit, a vplurality vof electric valves each including an anode, a cathode and a control member, means connecting vthe anode-cathode 'circuits of said electric valves for energization :from la Asupply of lalternating voltage so that .the valves are 'ar-- ranged in tivo groups with one tgroup rconnected to conduct during half cycles of voltage of one polarity and the other L'group connected to lconduct during ha-lf 'cycles of voltage vof the opposite polarity, meam's conductively connecting the control members-,of the valves 'of eachgroup respectively with 'the lanode-cathodecircuits vof diierent electric "valves ci the other group for transferring conduction initiated in `one of -said valves from valve Vto valve at the rate of one valve per half cycleof 'the alternating voltage, means for vdetermining t'he total number of said electric valves employed and for applying simultaneously 'to the control `members of selected ones of saidtotal number of electric valves a control voltage which renders `said selected ones of said electric valves conducting initially and establishesa pattern vof conduction by y,one of said electric valves which isxdependent on the number and location of said :electric valves initially rendered conductive, and means responsive to the pattern of conduction-by said vone of said valves vfor controlling the :operation of .said cir-cuit Icontrolling means.

6. In combination, Van alternating current supply circuit, a plurality of electric valves each having van anode, 4a cathode and a'control member, Imeans Iconnecting the lanode-cathode circuits of said kelectric valves for energization from said alternating current 'supply circuit so that rthey lare arranged Vin two groups With'one group .connected to conduct during half cycles 'of voltage of one polarity rand the other group connected to conduct during half cycles of voltage of thev oppcsite polarity, means for energizing the control members of each of said electric valves lof one Agroup for-conduction in response to conduction by a different electric valve of the other group and -withvccnduction by one of said electric valves causing successive conduction by said electric valves with the conduction advancing from electric valve to electric valve at Ythe rate of one electric valve per halfv cycle of the voltage of said supply circuit, and means for establishing the numberof successive half cycles of voltage of one polarity that one of the said electric valves conducts by simultaneously applying to 'the control members of more than one of said electric valves -a voltage :which simultaneously initiates conduction of said more than one of saidy electric valves.

7. A plurality of electric valves each including an anode, a cathode-and a control member, means- -for supplying'an alternating voltageito the anodecathode circutsof said electric valves so that the anodes of 'half of -said valves are positive during half vcycles of voltage of one :polarity and the conduction of one of said electric valves in accordance with the selection of a number of said electric valves in which conduction is simultaneously initiated, and means responsive to an initiating operation for applying to the control members ofsaid selected number of electric valves a voltage which simultaneously initiates conduction in said selected number of electric valves.

8. In combination, circuit controlling means for controlling the energization of a load circuit from an alternating current supply circuit comprising a plurality of electric valves each including an anode, a cathode and a control means,

means for supplying alternating voltage to the anode-cathode circuits of said electric valves, means energizing the control means of each of said valves in response to conduction by a different one of said valves for transferring conduction initiated in one of said valves from valve to valve at intervals dependent upon the periodicity of the alternating voltage impressed on said anode-cathode circuits, means for applying simultaneously to the control means of selected ones of said electric valves a control voltage which renders said selected ones of said electric valves conducting initially and establishes a pattern of half cycle conduction by one of said electric valves which is dependent on the number of said electric valves initially rendered conductive, and means responsive to conduction by said one of said electric valves for controlling said circuit controlling means to transmit current to said load circuit in accordance with the pattern of conduction established by said one of said electric valves.

9. In combination, circuit controlling means for .controlling the energisation of a load cir cuit from an alternating current supply circuit comprising a plurality of electric valves each including an anode, a cathode and a control means,

means for supplying alternating voltage to the anode-cathode circuits of said electric valves, means for energizing the control means of each of said valves in response to conduction by a.

different one of said valves so that conduction initiated in one of said valves progresses from valve to valve at intervals determined by the periodicity of the alternating voltage impressed on said anode-cathode circuits, means for impressing a voltage on the control means of selected ones of said valves to render the selected valves conducting initially, and means responsive to conduction by one of said valves for controlling said circuit controlling means to transmit current to said load circuit for a number of half cycles dependent on the number of electric valves selected.

10. In combination, a source of alternating current voltage, a plurality of electric valves each including an anode, a cathode and a control member, means 'connecting the anode-cathode circuits of said electric valves for energization from said source so that half of said valves are energized with voltage of one polarity and the other half with voltages of opposite polarity, means for energizing the control member of each of said. valves in response to conduction by a different one of said valves so that said valves trail one another in a closed loop, means for initiatm ing conductiopsimultaneously of a plurality kof said valves, and means responsive to the conductivity of one of said valves for effecting a circuit controlling operation during half cycles determined by the total number of valves employed and the number and location in the loop of the electric valves initially rendered conductive.

l1. An alternating current supply circuit, a plurality of electric valves each including an anode, a cathode and a control member, means connecting the anode-cathode circuits of said electric valves for energization from said alternating current supply circuit so that said electric valves are arranged in pairs connected in inverse parallel relationship, means connecting the control members of said electric valves so that the valves of each pair are energized in leading and trailing relationship and so that each pair of valves is in leading and trailing relationship With respect to other pairs of the system, means for initially rendering predetermined ones of said valves conductive so that each valve is rendered conductive for a number of half cycles determined by the number of valves initially rendered conductive and the half cycles of conduction are spaced in accordance with the location in the sequence of leading and trailing valves of the valves initially rendered conductive.

` 12. In combination, a pair of reversely connected electric valve means for transmitting alternating current to a load circuit from an alternating current supply circuit in a repetitive pattern measured in half cycles oi the supply circuit voltage, said pattern including a predetermined number oti half cycles of conduction by said valve means and a predetermined number of half cycles of nonconduction by said valve means, a plurality of electric valves arranged in two groups, means for energizing said valves from a supply of alternating voltage so that the Valves of one group may conduct during half cycles oi voltage of one polarity and the valves of the other group may conduct during half cycles of opposite polarity, means for controlling the "conductivity of each of the valves of each of said groups in response to conduction by a different one or the valves of the other of said groups so that conduction initiated in any one of said valves advances from valve to valve at the rate of one valve per half cycle of the alternating voltage, the number of said valves `being equal to the maximum number of half cycles in a repetitive pattern to be established, means for initiating 'conduction simultaneously of predetermined ones of said valves, and means for controlling conduction of each oneof said electric valve means respectively in response to conduction by one of said valves in each group of said groups to transmit a repetitive pattern of current to said load circuit determined by the number and location in the sequence of the valves initially rendered conductive.

13. In combination, a pair of electric valve:` means each having an anode, a cathode and a control member and having their anode-cathode circuits reversely connected in parallel for transmitting alternating current to a load circuit from an alternating current supply circuit, means for controlling the Iconductivity of said electric valve means to transmit current to said load circuit in a repetitive pattern measured in half cycles of the supply circuit voltage, said pattern including a predetermined number of half cycles of conduction by said valve means and a predetermined number of half cycles of nonconduction by said valve moans, said means comprising plurality of electric valves arranged in two groups, each of said valves having an anode, a cathode and a control member, means for ener gizing the anode-cathode circuits of said valves from a supply of alternating voltage so that the valves `of 'one group may conduct during half cycles of voltage of one polarity and the valves of the other group may lconduct during half cycles of opposite polarity, means for energizing the control member of each of the valves of each of said groups in response to conduction by a diiferent one Aof the valves of the other of said groups so that conduction initiated in any one of said valves Yadvances from valve to valve at the rate of one valve per half cycle of the alternating voltage, the number of said valves being equal to theV maximum number of half cycles in a repetitive pattern-to be established, means for simultaneously energizing the icontrol members and thereby initiating conduction of more than one of said valves simultaneously, `means for pre- -establishing the number and location in the sequence of thefelectric valves initially rendered conductive by operation oi said last mentioned means to establish the pattern of conduction by said valves and means' responsive to conduction by one of said valves in each of said groups `for controlling respectively the energization of the control member and thereby the conduction of .each of said pair of reversely connected Aelectric valve means.

14. In combination, circuit controlling means for transmitting alternating current to a load circuit from an alternating current supply circuit, a plurality of electric, valves each including an anode, a cathode and a control member, means connecting the anode-cathode circuits of said electric valves for energization from a supply of alternating voltage so that the valves are arranged in two groups with one group connected to conduct during half cycles of voltage of one polaritynnd the other group connected to conduct during half cycles of voltage of the opposite polarity, said connections being arranged so that the voltage of the cathodes of the valves of each group is intermediate the voltage impressed on the anode-cathode circuits of the other group, an initiating bus, means for impressing an initiating voltage between the alternating current supply connection for the anodes of o-ne group of said valves and said initiating bus, means for energizing the control members of each of the Valves of said one group in response to conduction of a different one of the valves of the second of said groups so that 'conduction vof a valve-in said second group initiates conduction of a valve in said one group during the next half cycle of the anode-cathode voltage of said valves, switching means for selectively connecting the control members of each of said electric valves of said second group to said initiating bus and to said alternating current supply connection for the ancdes of said one group of said valves to render one of lsaid valves conducting in accordance with a pattern established by said switching means and means responsive to conduction by said one of said valves for controlling the operation of said circuit controlling means.

15. In combination, a plurality of electric valves each1 including an anode, a cathode and a control member, means connecting the anodecathode circuits of said electric valves for energization from a supply of alternating voltage so that the valves lare arranged in two groups with one group connected to conduct during half lcycles of voltage of one polarity and the other group connected to conduct during half cycles of voltage of the opposite polarity, means for energizing the control members of the Valves of each group respectively in response to conduction by a diierent one of the valves of the other group so that conduction initiated in one of said valves progresses from valve to valve and :means for selecting more than one of said electric valves of one of said groups and simultaneously impressing a -voltage on the control members of said selected valves to initiate conduction thereof and establish a pattern of conducting and ncnconducting valves which advances through the valves of each of said groups in sequence from valve to valve in response to said last mentioned means.

16. In combination, a plurality of electric valves each includingv an anode, a cathode anda control member, means connecting the anodecathode circuits of said electric valves for energization from a supply of alternating voltage so that the valves are arranged in two groups with one group connected to conduct during half cycles of voltage of one polarity and the other group connected to conduct during half cycles of voltage of the opposite polarity, said connections being arranged so that the voltage of the cathodes of the valves ci each group is intermediate the voltage impressed on the anode-cathode circuits of the other group, means conductively connecting the control members of the valves of each group respectively with the anode cathode circuit of a different one of the valves'of the other group so that conduction initiated in one of said valves progresses from valve to valve, an initiating bus, switching means for connecting the anode circuits of said last mentioned group directly with said supply connection or with said initiating bus to determine the electric valves to be rendered conducting initially, and means for supplying a single pulse of voltage to lsaid initiating bus in response to an initiating operation.

17. In combination, a plurality of electric valves each including an anode, a cathode and a control member, means connecting the anodecathode circuits of said electric valves for energization from a supply of alternating voltage so that the valves are arranged in two groups with one group connected to conduct during half cycles of voltage of one'polarity and the other group connected to conduct during half cycles of Voltage of the opposite polarity, said connections being arranged so that the voltage of the cathodes of the valves of each group is intermediate the voltage impressed on the anode-cathode circuits of the other groupymeans for energizing the control members of the valves of each group respectively in response to conduction by a different one of the valves of the other group so that conduction initiated in one of said valves progresses from valve to valve, an initiating bus, means for initiating an intating voltage between the alternating current supply connection for the anodes of one group and said initiating bus, and switching means for connecting the anode circuits of said last mentioned group directly with said supply connection or with sa-i'd initiating bus to determine the electric valves to be rendered conducting initially.

18. A control system for controlling the energization of a plurality of load circuits from an alternating current supply circuit through a plurality of circuit controlling means so that each load circuit is alternately energized and deenergized in accordance with the same repetitive current-time pattern with the pattern of each oi said load circuits displaced with respect to the others of said load circuits to distribute the demand 1 i' on the supply circuit evenly with respect to time, said system comprising a plurality vof electric valves each including an an'o'de, a cathode vand a control member, means connecting the anodecathode circuits of said electric valves for energization from said supply circuit so that half of said electric valves are energized with voltage of one polarity and the other half of said electric valves are energized with voltage of the opposite polarity, means for energizing the control member of each of said electric valves in response to conduction by a different one'of said electric valves so thatsaid electric valves conduct in sequence by trailing oriell'another in a closed loop at the rate of one electric valve per half cycle of the voltage of the supply circuit, means for simultaneously applying'a Voltage to the control elements of a predetermined number of said-electric valvesrto rendersaid predetermined number of electric valves initially conducting and thereby establish a repetitive pattern of conduction and nonconduction by different ones of said electric valves which are electrically displaced with respect to one another by an amount equal to the desired time displacement of venergization of said different load circuits, means for deriving control voltages from each of the circuits of said different ones oi said electric valves, and means for controlling said circuit controlling means associated with each of said loads in response to one of said control voltages.

19. A control system for controlling the energization of a plurality of load lcircuits from an alternating current supply circuit through a plurality or circuits controlling means so that each load circuit is alternately energized and deenergized in accordance with the same repetitive time pattern with the pattern of each of said load circuits displaced with respect to the other of said load circuits to distribute the demand on the supply circuit evenly with respect to time, said system comprising a plurality of electric valves each including an anode, a cathode and a control means, means for supplying alternating voltage to the anode-cathode circuits of said electric valves, means for energizing the control means of each of said electric valves in response to conduction by a different one of said electric valves so that conduction initiated in one of said electric valves progresses from valve to valve at intervals determined by the periodicity of the alternating voltage impressed on said anode-cathode circuits, means for impressing a voltage on the control means of selected ones of said electric valves to render the selected valves conducting initially, and means for controlling said circuit controlling means associated with each of said loads in response to a control voltage derived from the circuit of different ones of said electric valves so that the patterns of control voltage and the patterns of load current of said different load circuits are displaced in time with respect to one another in accordance with the location in the sequence of said different ones of said electric valves controlling said different circuit controlling means.

20. In combination, a plurality of electric valves each including a pair of principal electrodes and a control member, means for connecting the principal electrodes of each of said valves for energization from an alternating current supply circuit, the control member of each of said electric valves being 4'connected to the anode circuit of another of said values so that conduction initiated in one of'said valves progresses from valve to valve in a 'closed loop in s'ynchroriism with'tlie voltage of the supply circuit, and means for selecting and simultaneously applying tothe ccntrol members of more than one of said electric valves a control-voltage which renders'said selected valves initially conducting and thereby establishes a pattern of conduction Aby one of said valves ldetermined by the number and location in the-sequence ofthe valves initially rendered conductive.

21. In combination, a supply of alternating voltage, a plurality of electric valves each including an anode, a cathode and a control member, means connecting the anode-cathode circuits of said electric valves for energization from Jsaid supply of alternating voltage so'that the valves are arranged in two groups with one group connected to conduct during half cycles of voltage of Vone polarity and the other group connected to conduct during half cycles of voltage of opposite polarity, said connections being arranged so that the voltage'of the'cathodes of the valves of each group is intermediate the voltage impressed on the anode-cathode Vcircuits of the other group, means providing inductive reactance connected in the anode circuit of each of said valves, and means connecting the control member of each one of the valves of one of said groups with the anode circuit of a different one of the valves of the other of said groups so that conduction initiated in one of said valves progresses from valve to valve in synchronism with the voltage of said supply circuit.

22. In combination, a supply circuit providing four different limits of alternating voltage, a plu.- rality of electric valves each including an anode, a cathode and a control member, means connecting the anode-cathode circuits of said electric valves for energization from said supply of alterhating voltage so that the valves are arranged in two groups with one group connected to conduct during half cycles of voltage of one polarity and the other group connected to conduct during half cycles of voltage of opposite polarity, said connections vbeing arranged so that the voltages of the cathodes of the valves of each group are at different limits and at a value intermediate the voltage impressed on the anode-cathode circuits of the other group, and means for controlling the energization of the control member of each one of the valves of one of said groups in response to conduction by a different one of the valves of the other of said groups so that conduction initiateL in one of said valves progresses from valve to valve in synchronism with the voltage of said supply circuit.

23. In combination, a supply circuit providing four different limits of alternating voltage, a pair of electric valves each including an anode, a cathode and a control member, means connecting the anode-cathode circuits of each of said electric valves for energization from said supply circuit so that one of said electric valves is connected to conduct during half 'cycles of voltage of one polarity and the other of said electric valves is connected to conduct during half cycles of voltage of opposite polarity, said connections being arranged so that the voltages of the cathodes of each of said electric valves are at diierent limits and at values intermediate the voltage impressed on the anode-cathode circuit of the other of said electric valves, means for applying a control voltage to the Kcontrol member of one of said electric valves in circuit with the altermating voltage of said supply circuit between the cathode of said one of said electric valves and the anode of the other of said electric valves to render said one of said electric valves conducting., an inductive circuit between the anode of said one of said electric valves and its connection through said inductive circuit With said alternating current supply circuit, and means for connecting the control member of said other of said electric valves with the anode connection cf said one of said electric valves With said inductive circuit. i

K 24.` In combination, an alternating current supply circuit, a pair of electric valves each including an anode, a cathode and a control member, means connecting the anode-cathode circuits of each of said electric valves for energization from said supply circuit so that one of said electric valves is connected to conduct during half 4cycles of voltage o-f one polarity and the other of said electric valves is connected to Vconduct during' half cycles of voltage of opposite polarity, the connection of one of said electric valves being so arranged tha-t the voltage of its cathode is intermediate the voltage impressed on the anodecat'hode circuit of the other of said electric valves, an inductive circuit between the anode of said other electric valve and its connection with said alternating current supply circuit, means for connecting the control member of said one of said electric valves to the anode connection of said other of saidelectric valves with said inductive circuit so that conduction of said other electricvalve progresses to said one electric valve in synchronism with the voltage of the supply circuit, and means for applying avvoltage to the control member of said other of said electric valves to render said other of said electric valves conducting.

MAURICE E. BIVENS.

REFERENCES CITED The following references are of record in the Vle of this patent:

UNITED STATES PATENTS Number Name Date 2,084,186 Braden June 15, 1937 2,319,524 Undy May 18, 1943 2,372,017 Rogers Mar. 20, 1945 2,403,955 Schlesinger July 16, 1946 

